The breathing gas in a diver's closed-circuit breathing gas apparatus (or “re-breather” as they are also known) undergoes volume expansion as a diver ascends through a water column. As a result, there is an increase in pressure at the inhalation side of the breathing gas apparatus that makes it difficult for the diver to exhale. When the diver inhales during a time of increased breathing gas pressure, the breathing gas is forced into the lungs thereby increasing the risk of the very dangerous condition known as pulmonary over inflation syndrome. To address this problem, the diver can bleed off some breathing gas. However, by bleeding off breathing gas, a diver reduces the possible duration of a dive via a reduction in the amount of breathing gas. Another option is for the diver to wait at certain depths during an ascent until enough of the breathing gas is metabolized into carbon dioxide that is then absorbed by a material (e.g., sodalime). This reduces the volume of gas in the rig thereby reducing breathing gas pressure. However, this approach takes extra time.